Jacob "kurtextrem" Groß
@kurtextrem.de
Senior Performance Engineer @Framer · The INP optimization guy · webperf/UX/security · @kurtextrem on other platforms.
#PerfNow has incredibly interesting talks. Anyone who's serious about performance should join.
Proud that we at @framer.com are sponsors.
Proud that we at @framer.com are sponsors.
October 31, 2025 at 3:01 PM
#PerfNow has incredibly interesting talks. Anyone who's serious about performance should join.
Proud that we at @framer.com are sponsors.
Proud that we at @framer.com are sponsors.
⚛️ReactConf once again mentioned concurrent stores. What if I tell you, we have concurrent external stores today? (kinda)
My latest blog post explains:
👉 How to to pair `useSyncExternalStore` with `useDeferredValue` (and `useMemo`)
⚡ Why this can improve UX & INP during hydration
My latest blog post explains:
👉 How to to pair `useSyncExternalStore` with `useDeferredValue` (and `useMemo`)
⚡ Why this can improve UX & INP during hydration
October 17, 2025 at 4:15 PM
⚛️ReactConf once again mentioned concurrent stores. What if I tell you, we have concurrent external stores today? (kinda)
My latest blog post explains:
👉 How to to pair `useSyncExternalStore` with `useDeferredValue` (and `useMemo`)
⚡ Why this can improve UX & INP during hydration
My latest blog post explains:
👉 How to to pair `useSyncExternalStore` with `useDeferredValue` (and `useMemo`)
⚡ Why this can improve UX & INP during hydration
I don't have a sandbox, but we're using it on prod @ Framer.
September 15, 2025 at 7:27 PM
I don't have a sandbox, but we're using it on prod @ Framer.
PSA: There's an open bug in React 19.1 that emits a `` for every single `![]()
` tag on a page when you SSR: github.com/facebook/rea....
This can result in *tons* of preloads that are bad for LCP and also wastes network bandwidth/data.
This can result in *tons* of preloads that are bad for LCP and also wastes network bandwidth/data.
August 25, 2025 at 4:55 PM
PSA: There's an open bug in React 19.1 that emits a `` for every single `![]()
` tag on a page when you SSR: github.com/facebook/rea....
This can result in *tons* of preloads that are bad for LCP and also wastes network bandwidth/data.
This can result in *tons* of preloads that are bad for LCP and also wastes network bandwidth/data.
The "Performance" tab of DevTools shows compilation & parsing here - important: disable caching to avoid v8's byte cache!
The compile hint changes how early the compilation happens. If the main thread stalls while waiting for compilation to finish, the compile hint can have positive impact.
The compile hint changes how early the compilation happens. If the main thread stalls while waiting for compilation to finish, the compile hint can have positive impact.
April 30, 2025 at 9:14 AM
The "Performance" tab of DevTools shows compilation & parsing here - important: disable caching to avoid v8's byte cache!
The compile hint changes how early the compilation happens. If the main thread stalls while waiting for compilation to finish, the compile hint can have positive impact.
The compile hint changes how early the compilation happens. If the main thread stalls while waiting for compilation to finish, the compile hint can have positive impact.
An easy way to figure out if this might make sense to add for you: Open Chrome DevTools -> 3 dots -> More tools -> Coverage. The files with the least amount of unused functions right after a page load, will gain the most from this.
April 30, 2025 at 9:14 AM
An easy way to figure out if this might make sense to add for you: Open Chrome DevTools -> 3 dots -> More tools -> Coverage. The files with the least amount of unused functions right after a page load, will gain the most from this.
Chrome 136+ ships a new V8 version that supports a "compile hint", which makes V8 parse and compile all functions in that file eagerly.
Great for entry points – where you know all functions will very likely be used. Less so as 'one weird trick to make all your JS faster'.
Great for entry points – where you know all functions will very likely be used. Less so as 'one weird trick to make all your JS faster'.
April 30, 2025 at 7:13 AM
Chrome 136+ ships a new V8 version that supports a "compile hint", which makes V8 parse and compile all functions in that file eagerly.
Great for entry points – where you know all functions will very likely be used. Less so as 'one weird trick to make all your JS faster'.
Great for entry points – where you know all functions will very likely be used. Less so as 'one weird trick to make all your JS faster'.
Part 2 of my "How to improve INP" series is for library authors and devs working on React codebases.
We'll take a look at how to:
✨ Ensure great INP & UX after user interactions
🚀 Make hydration concurrent
💡 Get non-blocking useEffects, always
so that... your site outperforms jQuery instead.
We'll take a look at how to:
✨ Ensure great INP & UX after user interactions
🚀 Make hydration concurrent
💡 Get non-blocking useEffects, always
so that... your site outperforms jQuery instead.
December 2, 2024 at 4:07 PM
Part 2 of my "How to improve INP" series is for library authors and devs working on React codebases.
We'll take a look at how to:
✨ Ensure great INP & UX after user interactions
🚀 Make hydration concurrent
💡 Get non-blocking useEffects, always
so that... your site outperforms jQuery instead.
We'll take a look at how to:
✨ Ensure great INP & UX after user interactions
🚀 Make hydration concurrent
💡 Get non-blocking useEffects, always
so that... your site outperforms jQuery instead.
"Everyone experiences P99" - @anniesullie.bsky.social
... at subway stations, or flaky internet.
Understanding & monitoring that experience can make sense.
blog.chromium.org/2021/04/digg... #PerfNow
... at subway stations, or flaky internet.
Understanding & monitoring that experience can make sense.
blog.chromium.org/2021/04/digg... #PerfNow
November 15, 2024 at 4:32 PM
"Everyone experiences P99" - @anniesullie.bsky.social
... at subway stations, or flaky internet.
Understanding & monitoring that experience can make sense.
blog.chromium.org/2021/04/digg... #PerfNow
... at subway stations, or flaky internet.
Understanding & monitoring that experience can make sense.
blog.chromium.org/2021/04/digg... #PerfNow
Closing talk day 2 @ #PerfNow: @anniesullie.bsky.social showing how much time improving CWVs saved. I like how Alex's great talk at the closing of day 1 was a wake-up call and now we get to see the positive side of things as contrast.
November 15, 2024 at 4:17 PM
Closing talk day 2 @ #PerfNow: @anniesullie.bsky.social showing how much time improving CWVs saved. I like how Alex's great talk at the closing of day 1 was a wake-up call and now we get to see the positive side of things as contrast.